Value-added recycling of waste brick powder and waste sand to develop eco-friendly engineered geopolymer composite

The increasing construction and demolition waste exacerbates environmental pollution and natural resources face potential depletion due to unrestricted mining. To mitigate these two issues and maximize waste reutilization, this paper focused on synergistically utilizing recycled brick powder (RCP) as precursor and recycled sand (RS) as fine sand to develop an eco-friendly fully recycled engineered geopolymer composite (EGC). The feasibility was evaluated based on the flowability and mechanical properties. The variation mechanisms of the mechanical properties were revealed through meso- and micro-scale investigation. The sustainability was analyzed from environmental impacts and cost perspectives. The results indicated that RBP had the potential to improve flowability, mechanical strength, and especially tensile ductility. The 80 % RBP content achieved an ultra-high ductility of above 14 %. The increase in the fiber bridging complementary energy associated with RBP contributed to the tensile ductility. RBP refined the micro-crack width in the matrix, thus favoring the mechanical strength. The synergistic utilization of 80 % RBP and 100 % RS (RBP80-RS) showed satisfactory mechanical properties with around 50 MPa compressive strength, above 4 MPa tensile strength, and 4 % tensile ductility. Compared to the M45-ECC, the specific embodied energy, specific embodied carbon, and specific cost of the RBP80-RS decreased by 40 %, 30 %, and 30 %, respectively. The current findings offer a promising solution to the accumulated waste brick and waste sand and provide more options for raw materials of EGC.